Ovulation in a female rat is a consequence of a complex series of neuroendocrine events which is initiated by diencephalic structures and is manifested by the secretion of gonadotropins from the pituitary gland. The transformation of a neural impulse in the brain to the release of anterior pituitary hormones involves the possible interplay of neurons, glial cells, cerebral spinal fluid and biogenic amines within the hypothalamus. This project attempts to investigate the nature of these hypothalamic neuroendocrine interactions. Pituitary gonadotropin release can be observed by measuring gonadotropin concentrations in peripheral plasma with radioimmunoassay procedures. The changes in plasma gonadotropin levels will be used as an index to evaluate the experimental effects. Two elements of this investigation will focus upon the involvement of biogenic amines and of third ventricular cerebral spinal fluid to induce pituitary gonadotropin release. During one phase the biogenic amine content within specific hypothalamic regions will be altered by pharmacological methods to examine the effects on gonadotropin secretion. In another series of experiments the cerebral spinal fluid will be tested to determine if it contains hormonal factors which may induce gonadotropin release. Possible intrahypothalamic fiber connections which may be important in the control of ovulation and anterior pituitary secretions will also be investigated. Bibliographic references: Cramer, O. M. and C. A. Barraclough, Failure to detect luteinizing hormone-releasing hormone in third ventricle cerebral spinal fluid under a variety of experimental conditions. Endocrinology, 96:913, 1976.